Stroke is a leading cause of death and significant morbidity. Unfortunately, there is still a critical need for new ischemic stroke therapies to reduc this significant societal burden as tissue plasminogen activator (t-PA), the only FDA approved ischemic stroke pharmaceutical therapy, has a limited therapeutic window and engenders significant risk. Furthermore, experimental therapies based solely on neuroprotection have largely failed to translate to human stroke. Instead, better therapies may emerge from an innovative approach based on improved understanding of the brain's own post-stroke repair mechanisms - identifying and exploiting endogenous agents that are both neuroprotective and promote brain repair. To this end, we have recently determined that the c-terminal fragment of the extracellular matrix component perlecan, termed domain V (DV), is persistently generated after ischemic stroke. When exogenously administered as a recombinant protein, DV is both neuroprotective and angiogenic (a reparative process), culminating in the restoration of stroke affected motor function in rats and mice. Preliminary data now suggest that DV increases neuronal repopulation of the infarcted and ischemic areas in vivo, and enhances neurite extension and connectivity in vitro. Furthermore, we have recently demonstrated that DV treatment suppresses glial scar formation in the ischemic core, thereby alleviating a potentially significant barrier to neuronal regeneration. Therefore, we hypothesize that post-stroke administered DV will provide a lasting, stable recovery, in part, by increasing the amount of new neurons that reach and establish themselves at the injury site. To that end, we now propose the following specific aims: 1) Determine the effect of long-term DV stroke therapy on neuronal repopulation and connectivity in the infarcted and ischemic areas, 2) Determine in mechanistic detail the potential of DV to influence neurite extension in vitro. For specific aim 1, stroke willbe induced by transient focal cortical ischemia using the tandem ipsilateral common carotid and middle cerebral artery occlusion model in 3-month-old male C57/Bl6 mice. BrdU injection followed by motor tests and immunohistochemistry of the infarcted and ischemic areas for BrdU and neuronal markers 4-8 weeks post-stroke will be performed to determine if DV, initially administered 7 days after stroke to minimize the influence of its neuroprotective effect, provides stable recovery and neuronal repopulation. Signs of animal illness will be monitored to assess potential adverse effects of long-term DV treatment. For specific aim 2, DV's effects on neurite extension and the potential role of the previously identified neuronal DV receptor, alpha2beta1 integrin, will be determined via neurite extension assays with wild-type or alpha2beta1 null adult mouse neurospheres. The successful completion of these studies will be significant by providing new insight into the brain's response to ischemic injury, and by further supporting our long-term goal of establishing DV as a novel stroke therapy for humans.